A group of investigators from the Department of Biology at Washington University involved in a wide range of cell and molecular biology research programs requests funds to purchase a Zeiss Axiomat light microscope equipped for bright-field, dark-field, phase contrast, differential interference contrast, epifluorescence, polarization and reflected bright field microscopy, plus the accessories required to permit use in the inverted (as well as the conventional) configuration. The microscope would be installed and operated in a suite adjacent to the existing departmental EM facility and would be available for use by all members of the department, but with priority being to the members of the user group specified in the proposal. About 2/3 of the time the instrument would be utilized in the conventional configuration for observational studies related to the ongoing research projects of the major users--for example, immunofluorescent localization of cellular antigens, high resolution in situ hybridization to determine chromosomal localizations of cloned DNA sequences, stroboscopic flash analysis of flagellar beat patterns, etc. The remainder of the time--and on a schedule announced well in advance--the microscope would be available in the inverted mode for observational purposes or for use with a microinjection apparatus the department plans to purchase. Microinjection would be used primarily for intranuclear injection of cloned DNA sequences (in order to achieve genetic transformation) and secondarily for injection of fluorescent antibodies into living cells.